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Caption

Streptococcus pneumoniae. Coloured transmission electron micrograph (TEM) of a section through Streptococcus pneumoniae bacteria. These Gram- positive bacteria are spherical in shape (cocci) and non-motile. They are usually found in pairs, as here, but do form short chains or clusters. The cell wall is visible with inner cell contents appearing granular. They secrete a capsule which is associated with certain pathogenic states. Streptococcus pneumoniae occurs both as a healthy commensal and a pathogen in the human respiratory tract. When pathogenic, it is a cause of pneumonia, pleurisy, peritonitis and meningitis. Magnification: x24,000 at 6.45cm size.